In general, a fiber optic transceiver is a communications device having an optical interface and an electrical interface. The optical interface transmits and receives fiber optic signals (e.g., through a set of fiber optic cables). The electrical interface transmits and receives electrical signals (e.g., through a circuit board connector mounted to a printed circuit board or PCB).
X2 and XENPAK are standard “off-the-shelf” fiber optic transceiver packages which are optimized for IEEE 802.3ae Ethernet communications. The electrical interfaces of both X2 and XENPAK operate according to the parallel Ten Gigabit Ethernet Attachment Unit Interface (XAUI) protocol, and have seventy-pin electrical interfaces, but have different physical form factors. A XENPAK module is, for example, physically larger than an X2 module.
Small form factor pluggable (SFP or SFP+) modules are also standard “off-the-shelf” fiber optic transceiver packages which are optimized for high-speed fiber optic channel applications. Both SFP modules and SFP+ modules include electrical interfaces which operate according to a serial protocol, and have twenty-pin electrical interfaces which plug into a small form factor (SFF) host connector. The electrical interface of an SFP module operates according to a Serial Gigabit Media Independent Interface (SGMII), whereas the electrical interface of an SFP+ module operates according to a Serializer-deserializer Framer Interface (SFI) protocol. However, both SFP and SFP+ may have compatible physical form factors. In general, the physical form factor of an SFP or SFP+ fiber optic transceiver is smaller than an X2 or XENPAK fiber optic transceiver.